WASHINGTON (AP) — All through downtown Washington, the primary sound for several blocks was the beeping of forklifts unloading more fencing.

There were no cars or scooters and seemingly no tourists Wednesday, just the occasional jogger and multiple construction crews at work. The U.S. Capitol that proved such a soft target last week was visible only through lines of tall, black fence.

Two blocks from the White House, a group of uniformed National Guard troops emerged from a tour bus and headed into a hotel as a state of lockdown descended on Washington that will last through the Jan. 20 inaugu...